The present invention relates to a semiconductor device manufacturing method, and in particular relates to a method of manufacturing a semiconductor device provided with a plurality of power semiconductor elements.
In inverter devices, uninterruptible power supply devices, machine tools, industrial robots, and other devices, semiconductor devices provided with a plurality of power semiconductor elements are used independently of the main-unit devices. Recently, in order to pass larger currents, there has been interested in wireless-structure semiconductor devices which do not use bonding wires (see for example Japanese Patent Laid-open No. 2004-228403).
FIG. 21 shows principal portions of a wireless-structure semiconductor device.
The semiconductor device 100 shown in the figure comprises a metal base sheet 101, insulating sheet 102 bonded onto the metal base sheet 101, and conductor patterns 103a, 103b, 103c, 103d patterned on the insulating sheet 102; a semiconductor element 105 is bonded via a solder layer 104b onto the conductor pattern 103b. 
Also, a transformer 106, capacitor 107, resistor 108, and other elements are electrically connected to the conductor pattern 103d via the solder layer 104d. And, an external leadout terminal 109, which leads to outside the semiconductor device 100, is electrically connected to the conductor pattern 103a via the solder layer 104a. 
Here, the semiconductor element 105 is a vertical-type power semiconductor element, configured with the electrode on the rear-face side connected to the conductor pattern 103b via the solder layer 104b. 
Also, in the semiconductor device 100, a print board 110 faces the metal base sheet 101. On the print board 110 are provided a through-hole 110a and conductor patterns 111 and 113.
And, a post electrode 112a which is electrically connected to the conductor pattern 111 is bonded to an electrode on the upper-face side of the semiconductor element 105, via the solder layer 104e. Further, a post electrode 112b electrically connected to another conductor pattern 111 is bonded to the conductor pattern 103c via the solder layer 104c. And, a control IC 114 is mounted on the conductor pattern 113.
In this way, in a semiconductor device 100, a wireless structure is employed, and the upper-face side electrode of the semiconductor element 105 and the conductor pattern 103c are electrically connected to the print board 110 via the post electrodes 112a and 112b. 
However, in the above-described solder layer 104e, since ordinarily paste-form solder material comprising a flux component is applied to the electrodes of the semiconductor element 105 using a printing method, so that after reflow, flux cleaning of the electrode surface has been necessary. And, because the solder material is in paste form, during reflow, there has been a problem of scattering of the flux component or solder material.
Also, the recent miniaturization of semiconductor elements have been accompanied by reductions in the weight of the semiconductor elements 105 themselves, so that when paste-form solder material is applied using a printing method, the semiconductor element 105 moves, and there is a problem of the occurrence of variations in the position of application of the paste-form solder.
Further, there are variations in the heights of the post electrodes 112a. As to post electrodes having relatively short distances, there has been a problem that the lower portion of the post electrode cannot be adequately bonded to an electrode via a solder layer.
This invention has been made in light of the above problems. This invention has as an object the provision of a semiconductor device manufacturing method enabling manufacture of semiconductor devices of high reliability and excellent operating characteristics, and high production yields.
Further objects and advantages of the invention will be apparent from the following description of the invention.